1. Field of Disclosure
The present disclosure of invention relates to a photolithography exposure apparatus having a variable length exposure blind and a method of operating the exposure apparatus. More particularly, the present disclosure relates to an exposure apparatus having a variable length exposure blind as used for providing photolithographic exposure to a fed-through mother substrate where the method of operation is capable of preventing formation of a shadow stain on the substrate resulting from moving of the variable length blind whereby elimination of the stain can improve quality of Liquid Crystal Display (LCD) substrates or other substrates whose monolithically integrated structures are formed by the exposure apparatus.
2. Description of Related Technology
Generally, a liquid crystal display (LCD) apparatus includes an LCD panel having two monolithically integrated substrates, namely, a thin film transistors (TFTs) containing substrate, and a color filters containing substrate. The two substrates are disposed opposite to and spaced apart from each other. A liquid crystal material layer is interposed between the TFTs substrate and the color filters substrate.
The TFTs substrate and the color filters substrate generally each has a multi-layered and monolithically integrated structure that is formed by use of one or more of a photolithography mask creating step, an exposure step that utilizes the photomask and an etching or other pattern development step that converts the photolithographically created image pattern into a structural pattern on the in-process substrate.
In the exposure step, light is irradiated onto a substrate, upon which for example, a light sensitive photoresist (PR) layer is coated, where the irradiated light first passes through a photomask having a specific imaging pattern. The photoresist layer is caused to chemically change (react) in accordance with the mask-passed light and to thus form a developed pattern thereon according to an exposure pattern formed on the photomask.
To decrease a cost for manufacturing each individual liquid crystal display apparatus, many LCD panels (daughter panels) are often simultaneously formed on a single mother substrate. However, the size of mother substrates tends to increase over time so that more liquid crystal display panels may be economically formed in one manufacturing process. However, with increase of the size of the mother substrate, a size of the corresponding photomask may be also increased such that the cost for manufacturing the liquid crystal display apparatus may be increased due to need to create photomasks of ever increasing sizes.
Recently, it has been proposed that a relatively small photomask be employed for a much larger mother substrate during the exposure process in order to avoid need for gargantuan mother-sized photomasks. In the proposed small mask type exposure process, the mother substrate is exposed using a plurality of sequential exposures to one or more small-sized photomasks, where the photomask(s) is/are moved about in between the exposures to thus expose different areas of the larger mother substrate. In an alternate embodiment, the mother substrate is moved relative to the photomask(s). In yet another alternate embodiment, both of the mother substrate and the photomask(s) are moved relative to each other.
Thus during any given exposure step, the mother substrate has an exposed area which is exposed to a given photomask and a non-exposed area that is not exposed to that given photomask. The photolithography exposure apparatus includes a movable light-blocking blind that for example blocks exposure of a second half of a corresponding window area of the substrate to thus prevent the blind-covered second area from being exposed while a first area is exposed to a half-sized photomask. Then the blind is moved from the second side of the exposure window to the first side of the exposure window to thus unblock the previously blocked second area while covering up the already exposed first area. After both halves of the mother substrate have been exposed to the pattern of the half-sized photomask, the blind is returned from the second side back to the first side of the exposure window in preparation for processing a next supplied, mother substrate or portion of the mother substrate.
However, in the so-proposed photolithography exposure apparatus, the exposure light is kept turned on all the time and when the blind is returned from the second area to the first (or alternatively, the mother substrate is translated into its second half exposure state), some sub-areas of the mother substrate are temporarily exposed more so to the irradiating light than are others and accordingly, a shadow stain may be shown in the overall exposed area of the mother substrate due to different amounts of exposure.
When the stain is relatively serious, the display quality of a liquid crystal display panel produced from the so-processed mother substrate may be deteriorated. Even if the stain is not relatively serious, the stain may be a noise factor that impedes detecting of other display errors. Thus, the display quality may be deteriorated.
It is to be understood that this background of the technology section is intended to provide useful background for understanding the here disclosed technology and as such, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to corresponding invention dates of subject matter disclosed herein.